C++ PATCH for c++/78139, private destructor and new-expression

[Jason Merrill]

The C++17 copy elision code in build_special_member_call was creating
a temporary and then eliding the copy directly, but creating that
temporary meant building a cleanup, which requires the destructor to
be callable.  And we shouldn't require that when building a
new-expression.  Fixed by using the new tf_no_cleanup flag.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit f41a463a7fba438a5127dc15e1043f287a16e9ad
Author: Jason Merrill <ja...@redhat.com>
Date:   Sun Feb 19 20:41:23 2017 -0800

            PR c++/78139 - destructor needed by new-expression
    
            * call.c (build_special_member_call): Use tf_no_cleanup.

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index d6d3a8f..93fae0d 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -8356,9 +8356,15 @@ build_special_member_call (tree instance, tree name, 
vec<tree, va_gc> **args,
       /* FIXME P0135 doesn't say how to handle direct initialization from a
         type with a suitable conversion operator.  Let's handle it like
         copy-initialization, but allowing explict conversions.  */
+      tsubst_flags_t sub_complain = tf_warning;
+      if (!is_dummy_object (instance))
+       /* If we're using this to initialize a non-temporary object, don't
+          require the destructor to be accessible.  */
+       sub_complain |= tf_no_cleanup;
       if (!reference_related_p (class_type, TREE_TYPE (arg)))
        arg = perform_implicit_conversion_flags (class_type, arg,
-                                                tf_warning, flags);
+                                                sub_complain,
+                                                flags);
       if ((TREE_CODE (arg) == TARGET_EXPR
           || TREE_CODE (arg) == CONSTRUCTOR)
          && (same_type_ignoring_top_level_qualifiers_p
diff --git a/gcc/testsuite/g++.dg/init/new48.C 
b/gcc/testsuite/g++.dg/init/new48.C
new file mode 100644
index 0000000..528a582
--- /dev/null
+++ b/gcc/testsuite/g++.dg/init/new48.C
@@ -0,0 +1,18 @@
+// PR c++/78139
+
+struct A
+{
+  A(int);
+private:
+  ~A();
+};
+
+struct B
+{
+  B(void*);
+};
+
+int main()
+{
+  B(new A(42));
+}